Improved Photocatalytic Water Splitting Activity of Highly Porous WO3 Photoanodes by Electrochemical H+ Intercalation

WO3 photoanodes are widely used in photoelectrochemical catalysis, but typically the as-synthesized material is annealed before application. It is therefore desirable to explore less energy-intensive treatments. In this study, WO3 films of up to 3.9 μm thickness were obtained by galvanostatic anodiz...

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Autores principales:	Ramunas Levinas, Natalia Tsyntsaru, Tomas Murauskas, Henrikas Cesiulis
Formato:	article
Lenguaje:	EN
Publicado:	Frontiers Media S.A. 2021
Materias:	intensity modulated photocurrent spectroscopy hydrogen intercalation tungsten oxide thin films anodization photoelectrochemical water splitting Technology T Chemical technology TP1-1185
Acceso en línea:	https://doaj.org/article/5218b6edae2a4b2592e08649b509316a
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spelling	oai:doaj.org-article:5218b6edae2a4b2592e08649b509316a2021-11-30T12:34:53ZImproved Photocatalytic Water Splitting Activity of Highly Porous WO3 Photoanodes by Electrochemical H+ Intercalation2673-271810.3389/fceng.2021.760700https://doaj.org/article/5218b6edae2a4b2592e08649b509316a2021-11-01T00:00:00Zhttps://www.frontiersin.org/articles/10.3389/fceng.2021.760700/fullhttps://doaj.org/toc/2673-2718WO3 photoanodes are widely used in photoelectrochemical catalysis, but typically the as-synthesized material is annealed before application. It is therefore desirable to explore less energy-intensive treatments. In this study, WO3 films of up to 3.9 μm thickness were obtained by galvanostatic anodization of tungsten foil in a neutral-pH Na2SO4 and NaF electrolyte, also containing a NaH2PO2 additive (to suppress O2 accumulation on the pore walls). Additionally, the WO3 photoanodes were modified by applying a cathodic reduction (H+ intercalation) and anodic activation treatment in-situ. XPS spectra revealed that intercalation modifies WO3 films; the amount of W5+-O and O-vacancy bonds was increased. Furthermore, subsequent activation leads to a decrease of the W5+ signal, but the amount of O-vacancy bonds remains elevated. The as-prepared and reduced (intercalated & activated) films were tested as OER photoanodes in acidic 0.1 M Na2SO4 media, under illumination with a 365 nm wavelength LED. It was observed that thinner films generated larger photocurrents. The peculiarities detected by XPS for reduced films correlate well with their improved photocatalytic activity. Photo-electrochemical impedance and intensity modulated photocurrent spectroscopies were combined with steady-state measurements in order to elucidate the effects of H+ intercalation on photoelectrochemical performance. The reduction results in films with enhanced photoexcited charge carrier generation/separation, improved conductivity, and possibly even suppressed bulk recombination. Thus, the intercalation & activation adopted in this study can be reliably used to improve the overall activity of as-synthesized WO3 photoanodes, and particularly of those that are initially poorly photoactive.Ramunas LevinasNatalia TsyntsaruNatalia TsyntsaruTomas MurauskasHenrikas CesiulisHenrikas CesiulisFrontiers Media S.A.articleintensity modulated photocurrent spectroscopyhydrogen intercalationtungsten oxide thin filmsanodizationphotoelectrochemical water splittingTechnologyTChemical technologyTP1-1185ENFrontiers in Chemical Engineering, Vol 3 (2021)
institution	DOAJ
collection	DOAJ
language	EN
topic	intensity modulated photocurrent spectroscopy hydrogen intercalation tungsten oxide thin films anodization photoelectrochemical water splitting Technology T Chemical technology TP1-1185
spellingShingle	intensity modulated photocurrent spectroscopy hydrogen intercalation tungsten oxide thin films anodization photoelectrochemical water splitting Technology T Chemical technology TP1-1185 Ramunas Levinas Natalia Tsyntsaru Natalia Tsyntsaru Tomas Murauskas Henrikas Cesiulis Henrikas Cesiulis Improved Photocatalytic Water Splitting Activity of Highly Porous WO3 Photoanodes by Electrochemical H+ Intercalation
description	WO3 photoanodes are widely used in photoelectrochemical catalysis, but typically the as-synthesized material is annealed before application. It is therefore desirable to explore less energy-intensive treatments. In this study, WO3 films of up to 3.9 μm thickness were obtained by galvanostatic anodization of tungsten foil in a neutral-pH Na2SO4 and NaF electrolyte, also containing a NaH2PO2 additive (to suppress O2 accumulation on the pore walls). Additionally, the WO3 photoanodes were modified by applying a cathodic reduction (H+ intercalation) and anodic activation treatment in-situ. XPS spectra revealed that intercalation modifies WO3 films; the amount of W5+-O and O-vacancy bonds was increased. Furthermore, subsequent activation leads to a decrease of the W5+ signal, but the amount of O-vacancy bonds remains elevated. The as-prepared and reduced (intercalated & activated) films were tested as OER photoanodes in acidic 0.1 M Na2SO4 media, under illumination with a 365 nm wavelength LED. It was observed that thinner films generated larger photocurrents. The peculiarities detected by XPS for reduced films correlate well with their improved photocatalytic activity. Photo-electrochemical impedance and intensity modulated photocurrent spectroscopies were combined with steady-state measurements in order to elucidate the effects of H+ intercalation on photoelectrochemical performance. The reduction results in films with enhanced photoexcited charge carrier generation/separation, improved conductivity, and possibly even suppressed bulk recombination. Thus, the intercalation & activation adopted in this study can be reliably used to improve the overall activity of as-synthesized WO3 photoanodes, and particularly of those that are initially poorly photoactive.
format	article
author	Ramunas Levinas Natalia Tsyntsaru Natalia Tsyntsaru Tomas Murauskas Henrikas Cesiulis Henrikas Cesiulis
author_facet	Ramunas Levinas Natalia Tsyntsaru Natalia Tsyntsaru Tomas Murauskas Henrikas Cesiulis Henrikas Cesiulis
author_sort	Ramunas Levinas
title	Improved Photocatalytic Water Splitting Activity of Highly Porous WO3 Photoanodes by Electrochemical H+ Intercalation
title_short	Improved Photocatalytic Water Splitting Activity of Highly Porous WO3 Photoanodes by Electrochemical H+ Intercalation
title_full	Improved Photocatalytic Water Splitting Activity of Highly Porous WO3 Photoanodes by Electrochemical H+ Intercalation
title_fullStr	Improved Photocatalytic Water Splitting Activity of Highly Porous WO3 Photoanodes by Electrochemical H+ Intercalation
title_full_unstemmed	Improved Photocatalytic Water Splitting Activity of Highly Porous WO3 Photoanodes by Electrochemical H+ Intercalation
title_sort	improved photocatalytic water splitting activity of highly porous wo3 photoanodes by electrochemical h+ intercalation
publisher	Frontiers Media S.A.
publishDate	2021
url	https://doaj.org/article/5218b6edae2a4b2592e08649b509316a
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Improved Photocatalytic Water Splitting Activity of Highly Porous WO3 Photoanodes by Electrochemical H+ Intercalation

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